Monte Carlo study of a double-scattering Compton camera with GEANT4

Compton camera is considered to be a very promising imaging device in nuclear medicine and molecular imaging, nowadays. The current version of Compton camera uses two position-sensitive detectors, i.e., a scatterer and absorber. The segment size of the absorber, including the thickness, is kept relatively large to provide an adequate level of detection efficiency, which on the other hand, seriously limits the resolution of the Compton camera. In this study, the resolution of a Compton camera is improved by utilizing two scatterers instead of one, and one absorber. The new system is composed of two double-sided silicon strip detectors (5 cm×5 cm×0.15 cm, 16 strips on each side) as scatterers and one coaxial-type high-purity germanium detector (7 cm diameter, 7 cm length) as an absorber. To test our idea, the double scattering Compton camera was modeled by using the GEANT4 simulation toolkit. Our simulation model includes the details of the detector geometry, energy resolution, spatial resolution (i.e., detector segmentation), and energy discrimination levels of the scatterers and absorber. Doppler energy broadening was modeled by implementing the Penelope physics model in the GEANT4 toolkit. Our simulation shows very encouraging results. The resolution of the Compton camera was considerably improved by using two scatterers.